U.S. patent application number 10/636539 was filed with the patent office on 2004-07-22 for apparatus for accelerating electro-optical response of the display.
This patent application is currently assigned to Industrial Technology Research Institute. Invention is credited to Liaw, Ming-Jiun.
Application Number | 20040140985 10/636539 |
Document ID | / |
Family ID | 32710198 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040140985 |
Kind Code |
A1 |
Liaw, Ming-Jiun |
July 22, 2004 |
Apparatus for accelerating electro-optical response of the
display
Abstract
An apparatus for accelerating electro-optical response of the
display selects one of given internal or external driving voltages
to overdrive gray levels transitions from other levels to
neighboring darkest or brightest levels. A select controller is
settled in the digital-to-analog-converter of a data driver to
select internal or external given multi-reference voltages. It can
accelerate electro-optical response of liquid crystals by the way
of overdrive and resolve the failure to conventional overdrive of
the highest and lowest gray level code, achieving the goal for
increasing the electro-optical response of liquid crystal
display.
Inventors: |
Liaw, Ming-Jiun; (Hsinchu,
TW) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
|
Assignee: |
Industrial Technology Research
Institute
Hsinchu
TW
|
Family ID: |
32710198 |
Appl. No.: |
10/636539 |
Filed: |
August 8, 2003 |
Current U.S.
Class: |
345/690 |
Current CPC
Class: |
G09G 3/3696 20130101;
G09G 2340/16 20130101; G09G 2320/0285 20130101; G09G 2320/0252
20130101; G09G 2310/027 20130101 |
Class at
Publication: |
345/690 |
International
Class: |
G09G 005/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2003 |
TW |
092101181 |
Claims
What is claimed is:
1. A method and apparatus for accelerating electro-optical response
of the display wherein it not only improve the electro-optical
response of the display by the way of enlarging drive ability but
also resolve the drawback of overdrive around the brightest and
darkest gray level source code, comprising: a data modifier
receiving a plurality of bits of image data, and then generating
modified multi-bit image data and an overdrive-control-signal; and
at least one data driver receiving the modified image data and
overdrive-control-signal to generate various electric signals for
driving the display.
2. The method and apparatus for accelerating electro-optical
response of the display in accordance with claim 1, wherein the
data driver has a digital-to-analog-converter.
3. The method and apparatus for accelerating electro-optical
response of the display in accordance with claim 2, wherein the
digital-to-analog-converter in the device connects a plurality of
reference electric signals to generate more drive signals of
display.
4. The method and apparatus for accelerating electro-optical
response of the display in accordance with claim 3, wherein at
least the darkest gray level source code of
digital-to-analog-converter in this device has a plurality of
driving signals to select.
5. The method and apparatus for accelerating electro-optical
response of the display in accordance with claim 3, wherein at
least the brightest gray level source code of
digital-to-analog-converter in this device has a plurality of
driving signals to select.
6. The method and apparatus for accelerating electro-optical
response of the display in accordance with claim 3, wherein at
least the darkest and the brightest gray level source code of
digital-to-analog-converter in this device have a plurality of
driving signals to select.
7. An apparatus for accelerating electro-optical response of the
display wherein it not only increases driving signal differences by
data driver to improve the electro-optical response of the display
but also resolve the failure of overdrive around the brightest and
darkest gray level source code, comprising: a first memory unit
that stores image data of the present frame and read image data of
the previous frame at the same time; a second memory unit that
stores at least one overdrive strategy; a data modifier that
receives multi-bit image data and to continuously compares images
between the present frame and the previous frame, and then
generates modified multi-bit image data and at least one overdrive
control signal; and a data driver that receives image data and the
at least one overdrive control signal from the data modifier, and
then it can generate electric signals to drive the display.
8. The apparatus for accelerating electro-optical response of the
display in accordance with claim 7, wherein the date driver further
comprising: an electric driving signal generation unit connecting
to a plurality of reference electric signals and generating more
electric signals than the number of gray levels expressed by image
data; an electric driving signal selector connecting to a plurality
of electric driving signals generated by electric driving signal
generating unit and connected with input image data; a first switch
connecting the a plurality of driving signals of the darkest gray
level code; a second switch connecting a plurality of driving
signals of the brightest gray level code; and a select controller
connecting to the first switch and the second switch wherein it can
select one of the plurality of the driving electric signals
corresponding to the darkest and the brightest gray level codes, by
the switch.
9. The apparatus for accelerating electro-optical response of the
display in accordance with claim 8, wherein the select controller
receives the overdrive control signal and connects the switch
states between the first switch and second switch; therefore,
controls the first and second switches in terms of the overdrive
signal.
10. The apparatus for accelerating electro-optical response of the
display in accordance with claim 8, wherein the select controller
receives the overdrive control signal and connects the switch
states between the first switch and second switch; then controls
the first and second switches in terms of the combination state of
the overdrive control signal and at least one bit image data.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a device that could
accelerate the electro-optical response and a method for setting
multi-reference-voltage in digital-to-analog-converter of data
driver to achieve overdrive of liquid crystal display.
[0003] 2. Description of the Related Art
[0004] Conventionally, liquid crystal displays (LCDs) response
slowly to external driving voltages. Although some inventions were
disclosed to accelerate response of nematic liquid crystals, but
the proposed methods still have obvious vision defects. Among these
methods, the switching speed between fully-on and fully-off is high
enough. But for middle gray level transitions, the speed is still
insufficient. Another approach is developing new fast-response
liquid crystal materials, but it costs too much. Thus, a new method
to improve the electro-optical response of LCDs is still strongly
desired. The conventional technique of overdrive referring to FIG.
1 shows the basic concept of accelerating response time of LCDs. If
a pixel's present gray level source code, Gn, is not the same as
its previous gray level code, Gn-1 [(n-1)th frame], it means the
brightness of the pixel is supposed to be changed. If gray level
source code Gn is directly transmitted to data driver for driving
an LCD, the brightness variation curve is shown as the second curve
B of FIG. 1. Due to the slow response of liquid crystal molecules,
the pixel can't reach the target brightness within a frame-time. In
order to accelerate the response time of liquid crystal display, in
the conventional methods, the gray level Gn is converted to higher
gray level code Gn' on purpose and transmitted into data driver;
then the response of LC follows the third curve C, reaching the
target brightness just at the end of the frame. When the next gray
level code of the next frame [(n+1)th frame] is the same as Gn, it
means the brightness of the pixel should be kept the same;
therefore, overdrive is unnecessary. In this case, all to do is
transmit the present gray level source code Gn into data driver
without any modification.
[0005] The function blocks of a conventional method accelerating
response of LCDs is shown in FIG. 2. The gray level source code Gn
of the present frame is stored into memory 203 as well as
transmitted to a data modifier 205. The gray level source code
Gn-1, stored in the memory 203, of the previous frame is also
transmitted into data modifier 205. And then, wherein the judgment
is conducted about whether overdrive is necessary or not. If data
is different from that of the previous frame, the data modifier 205
read overdrive look-up table to enlarge voltage potential between
LC cells to achieve overdrive purpose. In this case, a new gray
level code Gn' is generated and then converted into the driving
voltage/electric current by data driver 207 and then sent to the
panel.
[0006] FIG. 3 illustrates a digital-to-analog-converter of N-bit
data driver used in the conventional technique. The data driver
receives multi-bit (for example, N) digital image data, and several
positive/negative polarity of reference-voltages (VG1, VG2, . . . ,
VGm). A series of design-in resistors generate 2.sup.N analog
voltages which correspond to 2.sup.N digital image codes and are
connected to the selector 301. According to the input digital image
code, an analog-voltage will be select from the 2.sup.N analog
voltages by the selector 301 and outputted to the panel through the
buffer 303.
[0007] In conventional technique, the overdrive is achieved by
changing the image's digital codes to enlarge voltage potential
between LC cells. Thus, the shortcoming of the conventional method
using N-bit data drivers is unable to overdrive the transitions
from any gray level to the darkest level marked as code zero or the
brightest level marked as code 2.sup.N-1.
[0008] To overcome the drawback, one possible approach is to use a
more-than-N-bit data driver to reach transitions from any gray
level to zero or 2.sup.N-1 by code mapping. The drawback of the
approach is that the die size of the kind of more-than N-bit data
driver is almost two times larger than N-bit data driver, meaning
that the cost is huge.
SUMMARY OF THE INVENTION
[0009] The invention is a device with a major goal of accelerating
the electro-optical response of display by giving at least two
internal or external reference-voltages to the darkest and the
brightest gray levels of a data driver. The invention not only
accelerates electro-optical response of LCDs by overdrive but also
compensates the drawback of the convention overdrive technique that
is unable to overdrive transitions from other gray levels to the
highest and lowest gray levels.
[0010] The invention features a data modifier that will not only
modify input image data but also will generate at least one
overdrive control signal. The overdrive control signal is used to
determine one of the at least two internal/external driving
voltages for the highest gray level of the data driver. Moreover,
the overdrive control signal is also used to determine one of the
at least two internal/external driving voltages for the darkest
gray level of the data driver.
[0011] These and other objectives of the present invention will be
described in further detail below.
[0012] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will be described in relation to the drawings,
whereon FIG. 1 illustrates a basic principle of accelerating
electro-optical response of LCDs of the prior art;
[0014] FIG. 2 illustrates a schematic block diagram of accelerating
electro-optical response of LCDs of the prior art;
[0015] FIG. 3 illustrates a schematic block diagram of a
digital-to-analog-converter of a conventional data driver used in
the prior art;
[0016] FIG. 4 illustrates a schematic block diagram of a
digital-to-analog-converter of a data driver for a device that
accelerates electro-optical response of display according to the
first embodiment of the present invention;
[0017] FIG. 5 illustrates a schematic block diagram of a system
that accelerates electro-optical response of display according to
the present invention FIG. 6 illustrates a schematic block diagram
of a data driver for a device that accelerates electro-optical
response of display according to the first embodiment of the
present invention;
[0018] FIG. 7 illustrates a schematic block diagram a data driver
for a device that accelerates electro-optical response of display
according to the second embodiment of the present invention;
[0019] FIG. 8 illustrates a schematic block diagram of a digital to
analog converter of a data driver for a device that accelerates
electro-optical response of display according to the second
embodiment of the present invention;
[0020] FIG. 9 illustrates a schematic block diagram of a digital to
analog converter of a data driver for a device that accelerates
electro-optical response of display according to the third
embodiment of the present invention;
[0021] FIG. 10 illustrates a schematic block diagram of a digital
to analog converter of a data driver for a device that accelerates
electro-optical response of display according to the fourth
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0023] Please refer to FIG. 4, it is a first implement example
illustration of digital-to-analog-converter for a device that
accelerates the electro-optical response of display. The
digital-to-analog-converter of the data driver receives N-bit
digital data, connecting to positive/negative polarity by a
plurality of reference voltages (VG1, VG2, . . . , VGm), and
through them generating multi analog voltages to show digit signals
on the display. A voltage divider 409 that contains a plurality of
resistors and/or capacitors can generate more-than-2.sup.N analog
voltages to drive displays. In conventional technique, the
transitions from other gray levels to zero or 2.sup.N-1 (i.e. the
darkest and the brightest gray level codes) can't be overdriven by
using a N-bit data driver. Such as this invention in FIG. 4, for
the highest and the lowest gray levels (code zero and 2.sup.N-1,
respectively), at least two driving voltages are given to each of
the both codes by external driving circuits or by internal data
driver. That means at least two driving signals can be selected by
the brightest image code, 2.sup.N-1. Also at least two driving
signals can be selected by the darkest image code, 0. To see in the
figure, the reference voltages of the darkest gray level are the
first reference voltage VG0 and the second reference voltage VG0',
both are for the transitions from other gray levels to the lowest
gray level; the reference voltages of the brightest level include
the first reference voltage VGm and the second reference voltage
VGm', both are for the transitions from other gray levels to the
highest gray level, 2.sup.N-1. Furthermore, both the second
reference voltages, VG0' and VGm', also can be used as the
overdrive reference voltages for the transitions from.other gray
levels to zero or to 2.sup.N-1, respectively.
[0024] When image changes, the invention is going to compare pixel
values between the present frame and the previous frame. For the
pixel occurring gray level transition, its pixel values will be
re-determined. The overdrive control signal 401 from the driving
system described below in this invention, uses different voltage
levels or electric currents to identify whether or not the
overdrive reference voltage of the second reference voltage VG0' of
the darkest gray level code or VGm' of the brightest gray level
code will be selected. If needed, the overdrive control signal 401
is set to a specific level (e.g. high level or high electric
current or positive electric current or low impedance), and the
first switch 405 and the second switch 407 of select controller 403
to select the second reference voltage VG0' of the darkest gray
level code or VGm' of the brightest gray level code. If overdrive
is not necessary, the overdrive control signal 401 is set to an
opposite level (e.g. low level or low electric current or negative
electric current or high impedance) and the first switch 405 and
the second switch 407 of select controller 403 to select the first
reference voltage VG0 of the darkest gray level code or VGm of the
brightest gray level code.
[0025] FIG. 5 is a circuit connection illustration for a device
that accelerates the electro-optical response of a display. The
system features receiving N-bit image information, then generating
at least (N+1)-bit signal. In the (N+1)-bit signal, N-bits is image
information and the other one is at least one bit signal 401
expressing whether overdrive is needed or not by the second
reference voltages VG0' of the darkest gray level code and VGm' of
the brightest gray level code, respectively.
[0026] The operation is as follows: receive N-bit gray level code
of a frame. Moreover, transmit them to memory 203 and data modifier
501.
[0027] The memory 203 includes two sets of memory units, one is the
first memory unit, it stores the data in the present frame, Gn, and
the previous frame, Gn-1; and the other one is the second memory
unit, it stores overdrive strategy that might be expressed as LUTs.
The data modifier 501 reads gray level code Gn-1 of previous frame
from the memory 203, and then comparing with the present image data
to judge whether and where (what pixel) overdrive is necessary.
[0028] Case (1): For pixels without gray level variation, the input
N-bit data is output by the data modifier 501; at the same time the
overdrive control signal 401 will be settled by modifier 501 to a
specific states (for example, low level or low electric current or
negative electric current or high impedance) to represent overdrive
for this pixel is unnecessary. And then the overdrive control
signal 401 will be sent to the data driver 503.
[0029] In contrast, for the pixels whose gray levels need to be
changed, the data modifier 501 re-determines the image code in
order to enlarge voltage potential or current between two-opposite
electrodes of the display and achieves overdrive according to
look-up table or interpolation or both of them or numerical
operation analysis. In such situation, two cases can be further
distinguished:
[0030] Case (2): If the gray level transition isn't from other gray
levels to the neighbor levels of the brightest or the darkest
region (including exactly the brightest and darkest) or it is not
necessary to overdrive the pixel via the overdrive reference
voltages such like the second reference voltage VG0 or VGm', the
overdrive control signal 401 is set to the same specific state in
case (1).
[0031] Case (3): If the gray level transition is from other gray
levels to the neighboring levels of the brightest or darkest level
(including exactly the brightest and darkest) and needs overdrive
by the second reference voltage VG0 or VGm', the overdrive control
signal 401 is going to set to a state in contrast to the previous
descriptions (for example, high level or high electric current or
positive electric current or low impedance). Then, the modified
N-bit image data and the overdrive control signal 401 will be sent
to the data driver 503 whose first embodiment is going to described
in FIG. 6 to drive panel 500.
[0032] FIG. 6 is the first example illustration of a data driver
503 for a device that accelerates the electro-optical response of
display. The image data from the data modifier 501 is transmitted
into data driver 503 (FIG. 5), and then is stored into the first
register 601 and is hold in the first latch 603. At the same time,
the overdrive control signal 401 is transmitted into the second
register 602 and latched by the second latch. One of the data bits
611 is further transmitted to select controller 403 to judge the
gray level transition is occurred close to or exactly at the
darkest or the brightest gray levels. For the case of close to or
exactly at the darkest level, the second reference voltage VG0'
will be selected; For the case of close to or exactly at the
brightest level, the VGm' will be selected. The selection is done
by the select controller 403. When an overdrive by the second
reference voltage VG0' or VGm' is needed, the first switch 405 and
the second switch 407, as shown in FIG. 4, will select the second
reference voltage VG0' or VGm' according to the combination result
of the overdrive control signal 401 and one of the data bits 611.
When VG0' or VGm' isn't need, the first reference voltage VG0 or
the first reference voltage VGm will be selected. Finally,
digital-to-analog-converter 400 outputs an analog driving voltage
or current to buffer 607 and then drive the pixels in the
displays.
[0033] FIG. 7 is the second implement example illustration. The
difference between the implement and the first one is that the
first switch 405 and the second switch 407 as shown in FIG. 4
selects the second reference voltage VG0' or VGm' only according to
the state of the overdrive control signal 401, not the combination
result of the overdrive control signal 401 and one of the data bits
611.
[0034] FIG. 8 is the second implement example illustration of
digital-to-analog-converter of a data driver for a device that
accelerates electro-optical response of display in this
invention.
[0035] Its voltage-divided circuit is constructed by a plurality of
resistors cooperated with a plurality of reference voltages.
[0036] Certainly, the highest and lowest gray level code in data
driver, are also given at lest two driving voltages, individually.
In FIG. 8, the first reference voltage VG0 and the second reference
voltage VG0' for the darkest gray level code (0) are connected by
resistor. The first reference voltage VGm and the second reference
voltage VGm' for the brightest gray level code (2.sup.N-1), are
also connected by resistor. Nevertheless, the voltage of VG0 (or
VG0') can be generated by other methods, such as
resistor-voltage-divider referring to the second-reference-voltage
VG0' (or the first-reference-voltage VG0), by
capacitor-voltage-divider, by resistor or capacitor combinations,
by step up or step down circuits. The voltage of VGm (or VGm') also
can be generated by the above-mentioned several methods.
[0037] Refer to FIG. 9, the third implement example illustration of
digital-to-analog-converter of a data driver for a device that
accelerates electro-optical response of display. In this example,
more than two driving voltages can be selected to overdrive the
transitions from other gray levels to the neighboring levels of the
darkest or brightest gray levels. Take 3 driving voltages as an
example, the first driving voltage VG0, the second driving voltage
VG0', and third driving voltage VG0" can be chosen for overdrive
purpose. When select controller 403 receive the
overdrive-control-signal 401, base on the swing of gray level
changes, the controller will select a proper driving voltage from
VG0, VG0'and VG0" On principle, around the brightest gray level
code `2.sup.N-1` also can have several driving voltages VGm, VGm'
and VGm" to be selected for overdrive purpose.
[0038] The fourth implement example illustration of a
digital-to-analog-converter is shown in FIG. 10. The analog driving
voltages are generated by a resistor-voltage-divider as shown in
FIG. 9. The select controller 403 can select different overdrive
voltages according to different states of the overdrive control
signal 401.
[0039] Detail above-explanations are about a device that
accelerates the electro-optical response of a display. The purpose
of accelerating the electro-optical response of liquid crystals is
achieved by way of generating a overdrive-control-signal to control
a plurality of external or internal driving voltages corresponding
to a specified gray level, darkest or brightest or both. To
integrate mentions above, it shows the purpose and efficacy of this
invention provided with advanced and value in industry. Meanwhile,
it's a new and hither to unknown invention in current market. So
apply for a patent base on patent law.
[0040] In accordance to the above mention, therefore, the foregoing
is considered as illustrative only of the principles of the
invention. Further, since numerous modifications and changes will
readily occur to those skilled in the art, it is not desired to
limit the invention to the exact construction and operation shown
and described, and accordingly, all suitable modifications and
equivalents may be resorted to, falling within the scope of the
invention.
* * * * *